Energy conservation in crash analysis

- May 20, 2020 at 12:10 am
  
  danisd
  Subscriber
  
  Hello! I'm trying to do a crash analysis of a car structure, but looking at the solution I've noticed that the total energy of the system is increasing, and also the work. What is the reason for that? Shouldn't energy be conserved?
  
  I think it has something to do with the interaction between the surfaces.The structure has a main surface and two others that should act like a stiffener, located inside the main one. They are connected by bonded contact. When the two stiffeners are removed I don't have the same problem.
- May 20, 2020 at 4:15 pm
  
  Wenlong
  Ansys Employee
  
  Hi Danisd,
  
  Can you please provide us a plot of your energies? I assume you are using Explicit dynamics (autodyn)?
  
  Regards,
  
  Wenlong
- May 20, 2020 at 5:04 pm
  
  danisd
  Subscriber
  
  Hi Wenlong!
  
  Yes, I'm using explicit dynamics.
  
  This is the plot of energies:
  
  Thank you!
- May 20, 2020 at 7:41 pm
  
  Wenlong
  Ansys Employee
  
  Hi,
  
  1. So in Explicit dynamics, the definition of total energy is the sum of internal energy and kinetic energy (Ref below). Looks like your total energy curve's shape matches the internal energy.
  
  2. For the purpose of energy accountancy, the contact energy is added to the work done on the system (Ref below).
  
  Ref: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v195/wb_sim/ds_Energy_Results.html?q=explicit%20dynamics%20energy
  
  Regards,
  
  Wenlong